This disclosure relates generally to devices and methods for supplying electric power to electric vehicle service equipment (“EVSE”) for charging electric vehicles. More particularly, this disclosure relates to devices and methods for interfacing with an existing local power supply, such as the power supply to a residence, to provide sufficient electrical power for EVSE.
When a home owner purchases an electric vehicle, the owner will need to install EVSE to supply electrical power for charging the battery power unit of the electric vehicle. The EVSE installations must meet national and electrical codes. While most garages or carports are equipped with an electrical outlet that typically supplies 120V AC at 15 amps, this power is typically inadequate to charge in a reasonable time the newer vehicles with larger batteries. It is practically required to supply these vehicles with 220V AC at 30 to 50 amps. This is easily accomplished in newer homes with power lines and service panels having ratings of 200 amps or more. However, the large majority of older homes typically have 100 amp service panels with little or no spare capacity. Installing new service lines and larger panels is a costly, time consuming process raising the initial cost of owning an electric vehicle to the point where it may not be economically affordable.
Likewise, electric vehicle owners who reside in multi-unit dwellings must address the issue of available power for charging the vehicle battery supply. Preferably, sufficient power can be made available without the addition of power supply capacity.
One solution to the problem is for the EVSE and a household utility to share the same breaker in the existing load center. However, this is contrary to electrical codes because when both devices call for power at the same time, the breaker would trip.
To prevent this problem and comply with electrical codes, it is advantageous to automatically switch the electrical power between the two loads, the utility and EVSE, so that they are not drawing large amounts of power at the same time. The automatic switching is a realistic and practical solution since concurrent usage of the utility and EVSE for significant time periods is ordinarily not required.